In the first essay, I examine the impact of the introduction of exchange traded funds (ETFs) options on the information related trading of index options. Two option pairs, NASDAQ 100 index (NDX) and ETF (QQQ, currently QQQQ ) options, and Standard and Poor's 500 index (SPX) options and S & P Depository Receipts (SPY) options, are studied. I test the hypothesis, based on the theory of Chowdhry and Nanda (1991), and Admati and Pleiderer (1988), that the information component of spreads for index options should decline after ETF options were introduced. The method of George, Kaul and Nimalendran (1991) is used to estimate the adverse selection proportion of log quoted spread and revenue from quoted spread. Primary results show that the adverse selection component of index options declines after the introduction of ETF options, and that the adverse selection component of options on index ETFs is greater than that of options on index, suggesting more informed trading for ETF options. The second essay examines whether the liquidity premium decreases as the costs of transactions decline. Nine liquidity measures are estimated to form liquidity deciles portfolios. I use several benchmark asset pricing models in fixed and rolling 36-month samples to estimate time variation liquidity premia. Surprisingly, the results show that the liquidity premium does not monotonically decline over time, and it increases in the period from 2001 to 2006. This is inconsistent with the implication of liquidity-adjusted capital asset pricing models (L-CAPM). It is likely that the liquidity premium is generated by size and book-to-market factors, rather than the liquidity factor.

This thesis investigates systematic liquidity risk and short-term stock price reaction to large one-day price changes. We study 642 constituents of the FTSALL share index over the period from 1st July 1992 to 29th June 2007. We show that the US evidence of a priced systematic liquidity risk of Pastor and Stambaugh (2003) and Liu (2006) is not country-specific. Particularly, systematic liquidity risk is priced in the London Stock Exchange when Amihud's (2002) illiquidity ratio is used as a liquidity proxy. Given the importance of systematic liquidity risk in the asset pricing literature, we are interested in testing whether the different levels of systematic liquidity risk across stocks can explain the anomaly following large one-day price changes. Specifically, we expect that the stocks with high sensitivity to the fluctuations in aggregate market liquidity to be more affected by price shocks. We find that most liquid stocks react efficiently to price shocks, while the reactions of the least liquid stocks support the uncertain information hypothesis. However, we show that time-varying risk is more important than systematic liquidity risk in explaining the price reaction of stocks in different liquidity portfolios. Indeed, the time varying risk explains nearly all of the documented overreaction and underreaction following large one-day price changes. Our evidence suggests that the observed anomalies following large one-day price shocks are caused by the pricing errors arising from the use of static asset pricing models. In particular, the conditional asset pricing model of Harris et al. (2007), which allow both risk and return to vary systematically over time, explain most of the observed anomalies. This evidence supports the Brown et al. (1988) findings that both risk and return increase in a systematic fashion following price shocks.